"Jack drives a gas-guzzling SUV 15,000 miles a year. It averages 10 mpg. His wife Jill drives an economy car the same distance. It gets 30 mpg. The couple wants to use less gasoline. They can afford to trade Jack’s clunker for an SUV that gets 13 mpg or trade Jill’s sensible car for a hybrid that gets 60 mpg.
Which trade would save the most gasoline?
—Michael McClendon, Austin, Tex.
Test your intuition before doing the math. Look at the choices and make an educated guess about what makes the most sense. The answer appears at the end of the column"